The resale value is lousy with the P series because there are tons of them out there. Every pawn shop seems to have one, or more. Used they are a good bargain. Like was mentioned before nothing elegant about them, but durable. Trigger is ok, not as nice as a 92F or old S&W Model 39.
They are cheap to buy, reasonably accurate and very reliable. I had both the 9mm and the 45 versions. Great for taking non shooters to the range. Great for self defense class training. Grate for run and gun combat games. If you drop it in the gravel, you will not feel like crying like you would with a $2000 custom pistol. Since they are the cheapest of the good pistols, they are a good value. If you buy one for $400 and 5 years from now can only get $300 for it, you are only out $100. If you buy a $900 pistol and five years down the road sell it for $650, that looks like high resale, but you are still out $250.
Have a Ruger P89 9mm myself. Like the others have said its nothing of beauty but great shooter. I like the durability and is a good gun to throw in the console of the truck on trips. I have also never found ammo it won't feed. I compare it to the AK of pistols. Would probably function fine after dipped in water and sand without being cleaned. I don't worry about the scratches and dings like i do on my Colt and Smith. I never worry about resale because i bought it to use and abuse. When i get done with it you won't want it anyway. LOL---Matt
Do better, there is EZ-9 import from Serbia. A lot of people do not now about. It is based on Sig-Sauer P226. Israel made copy of that Serb gun and named Golan as well as some other countries. That handgun is distributed by EAA of Florida. It is half price then Sig, but I can not see any difference, very well made gun. You can go with Glock also. Ruger made good wheel guns as S&W does. Wish you good luck.